The present invention relates to a grinding apparatus for grinding a work face of a work such as a cam using a grindstone.
In general, a camshaft (work) for driving plungers of an injection pump is provided with a plurality of cams that are disposed coaxially. Each of the cams has a recessed face for improving an engine characteristic, the recessed face being formed on a cam face of the cam. It may be preferable that a curvature of the recessed face is small.
As a process for forming such a cam face, there is an electric discharging machining or a grinding process using a belt or a grindstone. In the above working processes, the electric discharging machining suffers from problems of a poor mass-productivity and high cost due to wear of the tool. On the other hand, the grinding using the belt suffers from a problem that the belt is short wearing. In contrast, the grinding using the grindstone is superior in mass-productivity and cost of the tool.
As a grinder using a grindstone, there is an apparatus is disclosed in Japanese Patent Application Laid-open No. 60-213472, for example. This apparatus comprises a motor and a belt for transmitting a driving force of the motor to a grinding wheel.
There is another apparatus is disclosed in Japanese Patent Application Laid-open No. 8-243906. This apparatus comprises a grinding wheel directly mounted to a driving shaft of a motor and a tiltable mount for fixing the motor. The mount is inclined in grinding process of a cam of a camshaft so as to prevent interference with other adjacent cams.
However, when a diameter of the grinding wheel is decreased to grind the recessed face, the size of a contour of a driving mechanism for the grinding wheel is limited to prevent interference between the driving mechanism and the cam. Therefore, in the case of the former apparatus where the belt transmits the power of the motor to the grinding wheel, the belt can not transmit enough driving force to the grinding wheel.
The latter apparatus does not suffer from a problem of power transmission. However, in the case of the latter apparatus, it is necessary for the grinding process to relatively move the grinding wheel in the axial direction of the camshaft where the wide of the grinding wheel is substantially decreased to prevent interference with other adjacent cams. Therefore, the latter apparatus suffers from problems of a poor working accuracy and a short life of the grinding wheel.